By Chris Morris BBC Europe correspondent

It has been quite a year for the European Union.

It began with the euro becoming a common currency across 12 member states and much of western Europe.

It should end with invitations being issued to 10 countries to join the 15 current members of the EU. By any standards, 2002 will be a landmark.

Hang on to your hats - there could be some dramatic moments ahead

Because whatever your view - whether you passionately support European integration, whether you believe it is a disaster about to happen, or whether you find it all hopelessly dull - this is a real turning point for Europe. Nothing will be quite the same again.

If enlargement goes ahead on schedule, with the 10 new members joining in 2004, the EU will become the biggest single market in the world with more than 500 million consumers.

The continent will finally - and peacefully - be united, more than a decade after the fall of the Berlin Wall.

For the candidate countries themselves, it has been a long time coming.

Painful process

They have had to carry out reforms in all walks of life in order to adopt a mammoth 80,000 pages of EU legislation - from taxation to transport policy, from company law to consumer protection.

For the former communist states, in particular, the transformation from heavily-centralised economies to the liberal pro-market system has not been without pain.

There is still plenty to be done.

The European Commission has warned that it expects further progress in judicial reform, for example, and in the fight against corruption and economic crime.

Ireland is to hold a second referendum on enlargement

A monitoring system will be set up to ensure that the would-be new members focus on the task in hand even after membership negotiations have been completed.

The EU itself will also have to rethink fundamentally the way it does business.

That is why it has set up a Convention on the Future of Europe, chaired by the former French President Valery Giscard d'Estaing.

It is trying to work out how the union will function in its enlarged form and what its priorities should be. It also needs to re-engage an apathetic European public.

There will be some form of European constitution and there are also proposals for a high profile EU president to better represent Europe on the world stage.

There is also a fearsome battle going on behind the scenes to decide the balance of power between individual member states and trans-national institutions like the Commission and the European Parliament. The looming deadline of enlargement has been the catalyst for all these debates.

Negotiations continue

But there are several hurdles to jump before the EU can pat itself on the back at the end of this year.

The final negotiations on the financing of enlargement have not been completed.

Ireland could vote "no" later this month in a second referendum on the treaty which makes enlargement possible.

The prospect of Cyprus joining the EU while it is still divided and disputed between Greeks and Turks makes everyone very nervous.

So hang on to your hats - there could be some dramatic moments ahead.

But this is history in the making, and no-one ever pretended it would be easy.